Altair- I really like this name, it reminds me of science and magic, for some reasonAurelian- to me this feels like a nationality, like australian or a classification, like reptilianCato- this is a little harsh for me, but I like itCasimir- this really seems to fit the vibe you're going forDamien- eh, feels slightly evil, or bad to meEmrys/Ambrose - love both, Ambrose seems to fit what you're going for more, but I also really like EmyrysEvander- I really like this
Faramond- very beautiful, It feels wild, like a moorGabriel- only ok, It seems to common for youHadrian- this name seems slightly malicious, maybe because I remember seeing it as a top choice for an evil dictator name on the writers boardHector- I really love thisHerne- I really think you should use this since it was on your first list, you seemed so in love with itHugo- One of my favorites, but it seems to be more popular in the UKIdris- ok, feels feminine to meIsidore- same as Idris, but I still kind of like itLucius/Lucien - Feels kind of evilOliver - like, but I think is too popular for you, how about olivierOrlando- ok, but in the U.S. I think of the cityRainier- beautiful imagery, and I love the connection to family
Remiel- I really like this and the nn RemyRobin- this is on my list, I Love the robin hood imagery and the freeness associated with birdsRoland- I like thisRufus- It's ok, but it was the name of a naked mole rat on a TV show I watched as a kid, that's what I always think of, as well as RufusWainwrightSilvan- pretty, but in the U.S. There is a well known learning center by that nameTheron- Love, It seems free, but could be anything and seems like it would age wellTiberius- seems a little cold to meTristram- I quite like thisWeyland- This seems ok, but a little off to me, I'm sure it has great meaning

And I would eliminate Lucius. Much like, say, Sylvester, it has suffered from being the go-to villain name for too long (perhaps its proximity to Lucifer?). It looks and might be mistaken for 'luscious.' Lucy is a popular girls name, far far more popular than Lucian etc for boys, and it might lead to teasing.

To bring it down to the top 5 I'd cut:
Faramond (sounds too much like pheromone, and I think the natural NN that it would be shortened to (Fara) is very feminine)

and.... hmm... well.... maybe...

Rainier (but for me I grew up near Mt. Rainier in NW USA so it sounds so much like a place name for me, but if I didn't have that personal association I think this would be a cool name and I probably would instead cut out..........

Tiberius (I love old Roman names (a lot), but I find that there are many better ones out there with better meanings. This one has no real meaning, and I'm not a fan of what a shortened/natural nickname for him would likely become at school and such-- Ty-- whether you wanted that NN or not, I think it'd be pretty unavoidable at school since Tiberius is so long and there are no other natural NNs that I can think that come from it)